The unusual inheritance pattern of the courtship songs in closely related grasshopper species of the Chorthippus albomarginatus-group (Orthoptera: Gomphocerinae)

V.Yu. Vedenina (1), A.K. Panyutin (1) and O. von Helversen (2)

1)Institute for Information Transmission Problems, Russian Academy of Sciences, B. Karetnyi per. 19, Moscow 101447, Russia
2)Institut fur Zoologie II, Universitat Erlangen-Nurnberg, Staudtstrasse 5, D-91058 Erlangen, Germany


Abstract
Sibling species of the Chorthippus albomarginatus-group are outstanding among all European grasshopper species since they have an extremely elaborate courtship behaviour. Here, we present a genetic analysis of the courtship song differences between two closely related grasshopper species Chorthippus albomarginatus and Ch. oschei. Measurements of eight courtship song characters and one parameter of courtship visual display were compared among parentals, F1 and F2 hybrids, and backcrosses. Variation in one morphological character, the number of stridulatory pegs, was studied as well. The distributions of song phenotypes were more consistent with a type-III genetic architecture, which involves complementary or duplicate pairs of loci. We suggest that this type of architecture may provide the novel elements of the hybrid songs, even more complex than the parental ones, which may offer a new starting point for sexual selection. One parameter of the visual display appeared to be controlled by a single locus, but differences in other characters of visual display could be explained by a more complex inheritance pattern. Inheritance of the peg number differences was consistent with a simple polygenic additive model. Sex linkage and/or maternal effects were not detected for any trait. We found a disproportionate influence of the Ch. albomarginatus parent on most hybrid song characteristics and the visual display, and this may support a previously offered idea that Ch. albomarginatus is an ancestral form and Ch. oschei is a derived species.